The present invention relates generally to bundling and attachment apparatus and more specifically to a tie for forming a plurality of elongate objects into a bundle and holding a pair of objects together.
Cable ties formed of thermoplastic material have been developed during the last twenty years and such ties have become increasingly popular for a variety of bundling and attachment applications because of their relatively low initial cost and their ease of installation. For certain other applications, however, plastic ties have limitations when compared to ties formed of metal. More specifically, plastic straps tend to become brittle when used at low temperature and have less desirable aging characteristics than similar metal straps; e.g., when used in a high temperature, high humidity environment, plastic ties may exhibit some elongation. Additionally, plastic ties are inappropriate for certain nuclear powerplant applications since radiation can result in degradation of the plastic material thereby rendering the strap more brittle. Also where it is desired to use the tie as a load carrying member the metal tie is sometimes preferable since it has the greater tensile strength.
Several self-locking bundling devices formed from metal have been proposed. Typically they include a strap having a plurality of regularly spaced vanes struck from the blank from which the strap is formed and extending at an angle relative to the strap surface. After the strap is positioned to encompass the objects to be held, strap portions must be overlapped so that the vanes of the respective strap portions interleave. Generally a keeper is provided which encircles the overlapped strap portions to hold them in engagement. The locking vanes extend from either one or both surfaces of the strap. If the vanes extend from the surface of the strap disposed adjacent the held objects, the relatively sharp edges of the vanes could damage the objects, particulaly if they are insulated electrical conductors. Even if the vanes extended only from the surface of the strap disposed, in use, away from the conductors, the vanes could damage the insulation of conductors in other bundles where several bundles are run adjacent one another through a high density wiring area. Of course, the requirement of overlapping strap portions necessitates that such devices be significantly longer than the circumference of the bundle. Some bundling devices of this class include a keeper which is fixed to the strap. It will be appreciated that with this configuration forces required to thread the free end of the strap through the keeper are relatively high as a plurality of vanes must be simultaneously deflected. Reference may be made to U.S. Pat. Nos. 3,311,957, 3,694,863 and 3,964,133 which show examples of such prior art bundling devices.
Metallic hose clamps have been proposed which include a locking head joined to one end of the strap and have a locking tongue for reception in apertures spaced along the strap. The tongues used in these clamps are in the form of a short beam thus requiring relatively high threading force to deflect the tongue. Additionally, the tongue typically extends outside the locking head making the clamps inappropriate for use with a tool which severs the excess threaded portion of the strap flush with the locking head. Examples of such prior art hose clamps are shown in U.S. Pat. Nos. 3,189,961 and 3,748,697.